Intensified Maize Cultivation Enhances Malaria Transmission in Western Ethiopia African Studies Center, Boston University, Boston, Massachusetts Harvard School of Public Health, Harvard University, Boston, Massachusetts Ethiopian Ministry of Health/World Health Organization, Addis Ababa, Ethiopia Ethiopian Institute for Agricultural Research, Jimma, Ethiopia Introduction Results Satellite image of Omo-Nada Woreda 15 8 (Oromia region) in Western Ethiopia. 7 By the year 2020, maize is expected to become the dominant The apparent maize-malaria link is a surprising and unanticipated 14 11 Fourteen sites were chosen to be 13 6 12 food crop in Africa. The burden of malaria, in parallel, has consequence of the agro-ecological dynamics of a dramatic included in this study based on the progressively increased throughout much of that continent. Maize expansion of maize production in eastern and southern Africa presence of stable mosquito breeding 4 5 habitat(s) in close proximity to maize. In pollen has been shown to provide an important source of during the past two decades. The expansion of maize in Africa is 10 the northern lobe, tassels were removed 3 nutriment for developing mosquito larvae. Larvae feeding on a function of concerted efforts by national and multilateral policy 9 from maize just prior to pollen shedding 2 maize pollen develop more rapidly and are larger than larvae emphasizing high yielding improved maize varieties for human 1 (2006). No intervention took place in the 2006 feeding on other food sources. This potentially results in an food supply. seven sites in the southern lobe. North Lobe (blue) – detasseled increased mosquito abundance and longer-lived females, thus South Lobe (yellow) – no intervention Mosquito larvae that feed on maize develop to the pupal stage Interventions will be reversed in 2007. 2007 increasing the risk for malaria transmission. In addition, malaria Interventions will be reversed more rapidly, more frequently, and produce larger adults where transmission is highest in areas of intense maize cultivation in maize pollen is abundant than do those that have little access to western Ethiopia. Current trends in maize food production in sub- this food. In addition, an epidemiological link has been Enlarged image of study site #1. Saharan Africa, therefore, suggest that people living and working Mosquito Habitats A, B, & C demonstrated between intensification of maize cultivation and an Mosquito breeding habitats are on or near smallholder farms of maize production may indicated by the letters A, B, and C. increase in malaria incidence. These data strongly suggest a Notice the close proximity of the increasingly be burdened by malaria. maize relationship between the agro-ecology of maize cultivation and C maize to the mosquito habitat and Aim malaria by creating enhanced conditions for malaria transmission the location of the house where in regions with high maize productivity. maize adult captures took place. Pollen B A was removed from maize located To test the hypothesis that maize cultivation contributes to the In the Oromia region of western Ethiopia, we de-tasseled maize in within a 50 m radius of the increasing burden of malaria in sub-Saharan Africa, we prevented maize mosquito habitat, shown here by a 50 m radius around each of seven productive mosquito House #1 maize plants from shedding pollen during the malaria- breeding habitats, while seven additional sites were left to highlighted circles. transmission season in a village with intense endemicity. We pollinate naturally. We monitored mosquito abundance and seek to determine whether the force of transmission thereby is habitat productivity in all fourteen sites from July to October 2006. A team of Ethiopians reduced. The intervention (i.e. de-teaseling) will be reversed between the removed tassels from two groups in 2007. maize just prior to pollen shedding in the Methods In the early 1980’s, Ethiopia’s seven intervention sites. socialist government saw maize as Maize was then hand- We de-tasseled and hand-pollinated maize in seven sites with a high yielding field crop to pollinated to ensure a stable mosquito habitats located in Omo-Nada Woreda, Jimma replace labor-intensive teff and productive crop for the poor yielding sorghum. Maize Zone (Oromia Region) in western Ethiopia. In parallel, maize farmers. grown on seven additional sites in the same district were surpassed teff, barley, and sorghum as the major crop by the allowed to shed pollen naturally. We recorded the force of mid-1980’s. In 1995, maize malaria transmission and mosquito development continuously cultivation was further expanded in each site during the rainy season (July to October 2006). by the use of inorganic fertilizers, improved maize seeds, and Adult, pupae, and larvae were monitored bi-weekly. The following agronomic techniques. measurements were recorded to determine habitat productivity: The intensity of maize Adult Captures by CDC light trap cultivation was positively • No. and identity of female anophelines per trap and significantly correlated with malaria incidence. • No. blood fed/gravid/parity (age) The cumulative incidence of malaria in high maize Larvae and pupae were counted from each breeding site to determine productivity. • wing length (body size) cultivation areas was 9.5 Pupae were taken back to the lab and allowed to emerged to adults for further times higher than in areas analysis. CDC light traps were used to monitor mosquitoes in nearby homes bi- Larvae/Pupae with less maize. weekly. • Ratio of larvae/pupae for each site Conclusion • Pupae were brought back to the lab and allowed to emerge to adults for further analysis. The force of transmission of malaria in sub-Saharan Africa might be reduced if maize plantings were excluded from the immediate All female anophelines were preserved in 100% ethanol for PCR vicinity of the homes, or if an early variety of maize was planted analysis to assess mosquito species and Plasmodium infection. such that pollen shedding would occur prior to peek mosquito Sites were monitored on a bi-weekly basis throughout the growing development. Alternatively, local malaria transmission could be season of maize. markedly reduced by cultivating a GMO maize that sheds specific Map of Ethiopia anti-mosquito toxins in its pollen. Sample analysis is currently showing the location of underway. We anticipate that the de-tasselled sites will have the study sites in the reduced vector abundance, size, and infection rates. Oromia region (Jimma Zone) of western Ethiopia. Acknowledgements Example of maize being cultivated in areas with stable mosquito breeding habitats. This work was funded by a grant from the Rockefeller Foundation The adjacent home provides a place for adult mosquitoes to seek blood. and by Fogarty International. .